Avoid unit conversion errors with this simple trick!


Article by: Abhinav Tanksale, on 02 March 2022, at 09:55 am Los Angeles time

Can you imagine what would have happened if a NASA Mars orbiter had failed because of something so simple as a Unit conversion error? 

That's exactly what happened in 1999 when they lost an orbiter while en route to Mars. The problem was, one team used metric units of measurement and another team did not, resulting in overstressed guiding engines and subsequent navigation failure. 

While solving a large number of complex math problems, it is important not to let units confuse things. Even a minor error in conversion can have huge consequences if critical calculations are affected!

This only goes to prove how even during such challenging tasks some of us may not be paying close enough attention to detail, especially when we are so involved with solving problems under pressure that our mind simply stops operating at its full capacity.

This is why unit conversion in engineering, as well as scientific research, isn't just vital, and extremely necessary to becoming successful - but it's also painfully sticky.

So, is there a way to safely convert between units and avoid screwing up (like losing millions of dollars)? The answer is Yes, and this blog is just meant to show you how to do that!


The trick is to do the conversions as fractions.

Let's start with a simple example: Convert 3 km to m (3 kilometers to meters).

There are 1000 m in 1 km, so the conversion is easy, but let's follow a system.

  • Write the conversion as a fraction that equals 1

  • Multiply it out (leaving all units in the answer)

  • Cancel any units that are both top and bottom

We can write the conversion as a fraction that equals 1: [1000 m / 1 km] = 1 And it is safe to multiply by 1 (does not affect the answer): 3 km × 1 = 3 km

So now we can do this: 3 km × [1000 m / 1 km] = 3000 km · m / 1 km

The answer looks strange! But we aren't finished yet. We can cancel any units that are both top and bottom: 3000 km · m / 1 km = 3000 m So, 3 km equals 3000 m. Well, we already knew that, but we want to follow a system, so that when things get complicated (& they usually do) we know what to do!

Note: if you do it wrong (with the conversion upside down) you get this: 3 km × [1 km / 1000 m] = 3 km · km / 1000 m And that doesn't let us do any canceling!

To avoid this mistake for larger calculations follow the system explained above!

To do it mentally, practice using it on a regular basis for complex calculations so that it gets wired in your brain.

Keep rocking!

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